1. Technical Field
Embodiments of the present disclosure relate to a smart self-repair device and method of self-repairing a package, and more particularly to a technology regarding repair efficiency in a package repair operation.
2. Related Art
A Dynamic Random Access Memory (DRAM) is constructed by a plurality of memory cells which are arranged in the form of a matrix. If a fail occurs even in one memory cell among a plurality of memory cells, a semiconductor memory device is classified as a bad product since it cannot perform an operation properly. According to high integration and high speed operation of a semiconductor memory device, the probability of a failed cell to occur increases.
Therefore, a yield, defined as the ratio of the number of good chips to the total number of chips, serves to determine a manufacturing cost that is likely to decrease. Thus, research has actively been made for not only a method for high integration and high speed operation of a semiconductor memory device but also a method for efficiently repairing a failed cell in an effort to increase a yield.
As a method for repairing a failed cell, a technology of building in a repair circuit for replacing a failed cell with a redundancy cell is being used. In general, a repair circuit includes redundancy columns/rows which are arranged in columns and rows each constructed by redundancy memory cells. A redundancy column/row is selected instead of a column/row in which a fail has occurred.
That is to say, if a row and/or column address signal which designates a failed cell is input, a redundancy column/row is selected instead of a failed column/row of a normal memory cell bank.
Generally, in order to represent an address which designates a failed cell, a plurality of fuses to be cut are disposed. The address of the failed cell is programmed as the plurality of fuses are selectively cut.
Currently, in a DRAM, methods for repairing a failed cell are divided into a repair method in a wafer state and a repair method in a package state.
The wafer repair method is a method for performing a test and then replacing a failed cell with a redundancy cell at a wafer level. The package repair method is a method for performing a test and then replacing a failed cell with a redundancy cell at a package state.
In a conventional package self-repair mode, a repair operation is performed by using only a row redundancy, and a column redundancy is not used. Therefore, in the case where a column-oriented fail occurs, it is impossible to repair the fail, and a package yield cannot help but decrease.
Moreover, in order for saturation of package yield, wafer test conditions should be diversified, and a package yield checking process should be repeated a multitude of times. In such a situation, a yield ramp-up time lengthens, and multiple numbers of experimental equipment is needed.